class DictProperty(object):
    ''' Property that maps to a key in a local dict-like attribute. '''
    def __init__(self, attr, key=None, read_only=False):
        self.attr, self.key, self.read_only = attr, key, read_only

    def __call__(self, func):
        functools.update_wrapper(self, func, updated=[])
        self.getter, self.key = func, self.key or func.__name__
        return self

    def __get__(self, obj, cls):
        if obj is None: return self
        key, storage = self.key, getattr(obj, self.attr)
        if key not in storage:
            storage[key] = self.getter(obj)
        return storage[key]

    def __set__(self, obj, value):
        if self.read_only: raise AttributeError("Read-Only property.")
        getattr(obj, self.attr)[self.key] = value

    def __delete__(self, obj):
        if self.read_only: raise AttributeError("Read-Only property.")
        del getattr(obj, self.attr)[self.key]

若是用上面的类去装饰一个方法,例如:

@DictProperty('environ', 'bottle.request.cookies', read_only=True)

print "in test"

那么当使用a = self.test时，是使用的__get__函数，还是test本身？

__get__ 是指使用map[key]形式取值的实现吧